The present invention relates to a method and a device for determining the heat loss coefficient of a premises. Within the meaning of the invention, a premises is an individual house or a building, in particular for residential or tertiary use, or else a part of such a building, for example an apartment in a building with multiple floors.
The heat loss coefficient of a premises, denoted K, is equal to the heat loss power of the premises (in Watts) per degree (Kelvin or Celsius) of difference between the temperature of the air inside the premises and the temperature of the outside air. This coefficient K is representative of the energy performance of the envelope of the premises.
The heat loss coefficient K of a premises is influenced, on the one hand, by the heat losses by transmission through the walls of the premises and, on the other hand, by infiltrations of air. The heat losses by transmission are represented by a factor HT=UAT, where U is the heat transfer coefficient of the envelope of the premises, also called the specific heat transfer coefficient of the premises, and AT is the total area of the walls of the premises. The infiltrations of air into the premises are represented by a factor m′.Cp, where m′ is the air renewal flow rate and Cp is the heat capacity of the air. Consequently, the heat loss coefficient K is given by the relation:K=HT+m′.Cp=UAT+m′.Cp. 
The coefficient U is used, within the framework of thermal regulations such as RT 2005 in France or the regulation EnEV in Germany, to estimate the overall energy consumption of the premises. Its determination is useful in order to perform a diagnosis of the thermal insulation of a premises, in particular after its construction, to verify that the constructor has adhered to the standards in force in terms of thermal insulation both in terms of choice of materials and their implementation, or when a refurbishment of the premises is considered, with a view to evaluating the measures that should be taken to improve the thermal performance.
It is known to determine the heat loss coefficient of a premises by means of computational softwares which involve modeling the envelope of the premises. Such softwares are relatively tricky to implement and have the drawback of providing only a theoretical result, which does not assess such real parameters as the effective implementation of the insulation materials, the construction technology, etc.
Moreover, it is known to determine the heat loss coefficient of a premises by carrying out in situ measurements in the premises over long periods, which generally extend over several weeks or months, and then by undertaking a statistical analysis of these measurements. The statistical analysis is made necessary by the multiplicity of parameters which influence the thermal behavior of the premises over the measurement period, in particular the meteorological conditions and the occupancy conditions of the premises. These known in situ measurement methods have the drawback of being lengthy and of involving significant and expensive equipment.